Conventionally, there is widely offered the technique capable of treating graphics, marks, characters, illustrations and the like which are displayed on a screen of a display device as independent objects respectively and designating and selecting a desirable one of the objects by a pointing device such as a mouse. By applying the technique to select the desirable object, it is possible to cause a computer to execute a predetermined processing related to the selected object.
Moreover, there is also offered the technique for enlarging or reducing an image including the object. As shown in FIG. 1, in the case in which an image 104 including a plurality of objects 101 to 103 is reduced, the individual objects 101 to 103 included in the image 101 are reduced, and at the same time, an interval between the objects is also reduced. In some cases in which the interval between the objects is smaller than sizes of the objects 101 to 103, the reduced objects 101 to 103 overlap with each other when a reduction ratio is increased.
For example, in the case in which two objects overlap with each other, upper and lower portions which overlap with each other are generated according to a predetermined rule. In other words, a part of the object on a lower side is hidden under a part of the objects on an upper side. In this case, if a cursor of a mouse is placed over a portion in which two objects overlap with each other, the object on the upper side is selected. In order to select the object on the lower side, accordingly, it is necessary to place the cursor over a portion which is provided on the object at the lower side and does not overlap with the object on the upper side.
In some cases, however, the objects included in the image perfectly overlap with each other and the smaller objects are perfectly hidden under the greater objects when the image is reduced. In some cases, alternatively, at least three objects overlap with each other so that one of the objects is perfectly hidden under the other two objects or more. In such a state, there is caused a problem in that the object hidden under the other objects cannot be selected by means of a mouse.
There is proposed the technique in which a desirable object can be selected also in the case in which a certain object is perfectly hidden under the other objects (for example, see Patent Document 1). In the technique described in the Patent Document 1, a mouse cursor is placed over a portion in which two objects overlap with each other, and the object on the upper side is assumed to be selected when a left button of a mouse is pushed down and the object on the lower side is assumed to be selected when a right button of the mouse is pushed down.
Patent Document 1: Japanese Laid-Open Patent Publication No. 9-223241
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-299106
Patent Document 2: Japanese Laid-Open Patent Publication No. 2000-308370